The goal of this project is to compare two confocal line-scanning microscopes to a standard confocal pointscanning microscope for reflectance imaging of human skin in vivo. One line-scanner is based on a divided objective lens pupil and the other based on a full pupil configuration. Each configuration has advantages. The long-term objective is to create a fundamentally simpler class of confocal reflectance scanning microscopes for imaging human skin cancers for clinical and surgical dermatology. Every year, in the USA alone, 1.2 million new cases of skin cancers are diagnosed. Of the 5.5 million biopsies performed, 80% turn out to be normal and thus avoidable, costing US healthcare $1.65 billion annually. Confocal reflectance microscopy may enable screening and diagnosis of these skin cancers noninvasively and in real-time, with minimal need for biopsy. The hypothesis is that a confocal line-scanner with either a divided-pupil or a full pupil will be simple, and will provide very high resolution and optical sectioning. Such line-scanning microscopes may compete with today's state-of-the-art point-scanning microscopes for imaging human skin in vivo, for clinical diagnosis and surgical guidance applications. Preliminary results with a prototype confocal divided-pupil line-scanner demonstrate imaging of nuclear and cellular detail in the epidermis of human skin in vivo. The prototype is considerably less complicated than a point-scanner. The specific aims are to create a confocal line-scanner that combines both divided-pupil and full-pupil configurations. The combined divided-and-full pupil will enable experimental evaluation of their line spread functions (LSFs) and imaging performance under identical optical and skin conditions. Experimental comparisons of divided pupil and full-pupil LSFs to the confocal point spread function (PSF) will be made under two conditions: diffraction-limited (i. e., nominal instrument) conditions as well as scattering and aberrating conditions of actual skin (i. e., deep within human dermis, through full-thickness epidermis). Divided-pupil and full-pupil line-scanned images of human skin, both ex vivo and in vivo, will be compared to histology and to the well characterized images obtained by confocal point-scanners. Background noise and contrast in the images will be quantitatively compared between the two line-scanning and the point-scanning methods. RELEVANCE TO PUBLIC HEALTH Confocal reflectance microscopy may enable screening and diagnosis of skin cancers such as melanomas and basal- and squamous-cell carcinomas, or may guide surgery of such cancers, directly and in real-time on the patient. The diagnosis or surgical guidance may be noninvasive, with minimal need for biopsy, minimal pain and minimal expense. [unreadable] [unreadable] [unreadable]